In his latest post Anthony Ferrara is back with more discussion around the "only supporting the latest versions" debate (here is the previous article). In this new post he talks about being a "responsible developer" and how that relates to keeping your software up to date.

The general consensus [shared during a DevHell and PHPTownHall Mashup ] was that as an ideology, only supporting latest versions is correct. From a practical standpoint though they said that it's unrealistic. That there are tons of legacy systems out there that are running just fine and can't justify the cost of upgrading. So they shouldn't have to upgrade "for ideological reasons". From one point of view, this certainly makes sense. [...] This point of view disturbs me deeply. And it further disturbs me that it came from the same person who preaches for testing.

He makes the connection between being responsible and the software upkeep through testing. He points out that the real effectiveness of automated testing is in preventing regressions - that is, when software is updated, that bugs don't reappear. He then goes on to share his opinion on some of the other arguments presented in the recording like the "if it ain't broke, don't fit it" and security issues topics. He also shares some number of the reality of what can happen if software is not up to date (or even patched) and how this circles back around to his previous points about software versions driving the OS and PHP versions forward.